Operating on an ischaemic area is an established method during surgery on the limbs. Virtually all kinds of surgery on the knees, hands and ankles are carried out in an ischaemic area. The advantage with an ischaemic area is that no disturbing bleedings occur and that the surgeon therefore can better see the structures he is interested in. Thus the operation can be carried out quicker and with a greater anatomical certainty.
At the moment an ischaemic area is applied as follows; the limb is wrapped with so-called Esmarch's bandages. Said bandages are made of 1 dm wide, 5 m long and 1-3 mm thick rubber strips. The limb is hereby emptied of blood. The limb is wrapped tightly beginning from its end, i.e. the hand or the foot, and continuing towards the trunk to a point on the upper arm or the thigh, respectively, where a pressure cuff is applied. The pressure cuff is pumped up to a pressure of 50-100 mm Hg above the patient's blood pressure. The thicker the limb is, the higher the pressure needed to achieve ischaemia, if a cuff with a certain width is used. As the blood pressure can vary during the operation, an arm cuff is usually pumped up to 250-300 mm Hg and a leg cuff to 300-500 mm Hg if usual cuffs are used, whereby one is usually sure of keeping the operating area ischaemic. To avoid injuries caused by pressure, as low a pressure as possible is desirable. It is possible to operate in an ischaemic area for 11/2-2 hours without any clinical damage occurring. It has been shown that the first injuries to occur in an ischaemic area are pressure injuries on, above all, the nerves which pass under the cuff. The most obvious damages can be found in the tissue under the edges of the cuff. Here the pressure stresses are combined with a mechanical deformation of the tissues based on the so-called shear stresses, which are greatest under the edges of the cuff. It is therefore, desirable to keep as low a highest pressure as possible and to achieve a step-by-step reduction of the pressure towards the edges of the cuff. This can be achieved with a wide contact surface and two or more cuffs.
The problems that are connected with applying and keeping an ischaemic area by means of conventional techniques are:
It is troublesome, laborious and hazardous to empty blood from the limb with the Esmarch bandages. It has happened that front teeth have been knocked out when the elastic strips have burst.
The pressure cuffs and the control mechanism are expensive and not completely reliable.
Clinics that do not have sterile Esmarch bandages and pressure cuffs cannot apply a sterile ischaemic area. The time it takes to achieve an ischaemic area is then prolonged by the time of washing and preparation of the limb in question.
The cuff cannot be moved on the limb during an operation while maintaining the ischaemic area.